1. Field of the Invention
The present invention relates to chemical iodine lasers, and more particularly to a chemical laser system including an apparatus for generating atomic iodine.
2. Background Art
The mechanics of gas lasers are currently well known. Chemical lasers induce a lasing action by mixing an optically active lasing medium with an electronically excited energizing gas and then directing a flow of the resultant gaseous mixture into an optical laser cavity where the lasing action is generated. The lasing medium and the electronically excited gas react chemically to provide the necessary population inversion and lifetime required to create the lasing action.
In oxygen/iodine laser systems, iodine is utilized as the optically active medium and singlet delta oxygen, O.sub.2 (.sup.1 .DELTA.), as the energizing gas. The chemical generation of gaseous O.sub.2 (.sup.1 .DELTA.) is well known in the art. For example, U.S. Pat. No. 4,102,950 and U.S. Pat. No. 4,310,502 describe O.sub.2 (.sup.1 .DELTA.) generators and are incorporated herein by reference. The optically active lasing medium, iodine, must also be in the form of a gas or vapor in order to be mixed into the electronically excited energizing gas, O.sub.2 (.sup.1 .DELTA.). Under ambient conditions iodine exists as a solid in its molecular form, I.sub.2, which melts at 113.5.degree. C. and boils at 184.4.degree. C. Thermal energy must be supplied to the solid I.sub.2 to convert it to a vapor suitable for use in an oxygen/iodine transfer laser system.
An iodine laser is based on the electronic transition between excited atomic iodine and ground state atomic iodine according to the following equation: EQU I(.sup.2 P.sub.1/2).fwdarw.I(.sup.2 P.sub.3/2)+h.nu.(at 1.315.mu.)
Among the advantages of the iodine laser is emittance at a single frequency (1.315.mu.); the shortest wavelength yet attained by purely chemical means. The most common chemical method for producing the excited atomic iodine, I(.sup.2 P.sub.1/2) or I*, is well known in the art as disclosed in U.S. Pat. No. 4,267,526, incorporated by reference. The disclosed method consists of mixing molecular iodine vapor, I.sub.2, with electronically excited oxygen, O.sub.2 (.sup.1 .DELTA.). The mechanism by which I.sub.2 is converted to I* is believed to involve a number of steps and may be represented by the following equations: EQU 2O.sub.2 (.sup.1 .DELTA.).fwdarw.O.sub.2 (.sup.3 .SIGMA.)+O.sub.2 (.sup.1 .SIGMA.) EQU O.sub.2 (.sup.1 .SIGMA.)+I.sub.2 .fwdarw.O.sub.2 (.sup.3 .SIGMA.)+I.sub.2 * EQU I.sub.2 *.fwdarw.2I(.sup.2 P.sub.3/2) EQU I(.sup.2 P.sub.3/2)+O.sub.2 (.sup.1 .DELTA.).fwdarw.I*+O.sub.2 (.sup.3 .SIGMA.)
If all or a portion of the iodine mixed into the O.sub.2 (.sup.1 .DELTA.) were in the ground state atomic form, I(.sup.2 P.sub.3/2), an overall decrease in the amount of O.sub.2 (.sup.1 .DELTA.) would be required to attain the same concentration of I* in the gas mixture. However, the extreme corrosivity of thermally hot iodine is due primarily to the reactivity of atomic iodine. Consequently it has been more practical to atomize molecular iodine at relatively low temperatures using the excitation energy stored in the excited O.sub.2 (.sup.1 .DELTA.).
In the chemically driven oxygen/iodine transfer laser, the conventional source of iodine is the element itself transformed into a molecular vapor by applicaton of heat or by radiation as disclosed in U.S. Pat. No. 4,434,492. This physical process is extremely energy inefficient in that it requires the iodine supply to be kept hot continuously in order to be utilized on demand.